Method of treating aluminum alloys



Oct. 3, 1939. H. H. WETZEL METHOD OF TREATING ALUMINUM ALLOYS Filed Dec.11, 1935 F' 1 a6 Z6 I A? [-6 o 26 z/ A 0 0 um; 0 A9 /a By W PatentedOct. 3, 1939 UNITED STATES PATENT OFFICE 2,174,845 METHOD OF TREATINGALUMINUM ALLOYS Harry Herman Wetzel, Santa Monica, Calif., as-

signor to Douglas Aircraft Company, Inc., Santa Monica, Calif., acorporation of Delaware Application December 11, 1935, Serial No. 53,929

7' Claims.

- or bending operations and the aluminum alloy used must be in a softcondition in order that it may be shaped or formed without fracture orspring-back. The aluminum alloy in this soft condition is unsuited foruse in service because of low strength and inferior resistance tocorrosion. It is therefore necessary, after forming the parts, tosubject them to treatment which will chemically change the alloystructure in order to produce the optimum percentage of alloying elementin solid solution. When so treated there is imparted to the aluminumalloy the best possible physical properties and resistance to corrosion.Such treatment as practiced prior to my invention consists of heatingthe aluminum or aluminum alloy part or object to a predeterminedtemperature, holding the temperature for the necessary length of timeand thereafter cooling the object from the temperature range to which itwas heated. The rapid cooling as practiced prior to my invention wasordinarily done by plunging the objects into cold water. Such quenchingis effective in rapidly cooling the part and in producing properphysical properties and resistance to corrosion, but the ob-' ject sotreated is usually so seriously warped that it is not capable ofwithstanding the design stress. It has been the practice, therefore, tostrengthen such warped parts immediately after the quenching operationand before the metal has hardened to any great extent. This period isordinarily about thirty minutes and the work must be straightened withinthis period of time. In most cases, however, thirty minutes is notsuflicient to do all the straightening, and after a part has oncebuckled it is very difficult to bring it back to its original shape. Itwill therefore be seen that it is practically impossible to completelyand satisfactorily straighten a part or object particularly if thewarping is at all serious. Obviously such a method is undesirable fromthe standpoint of dependability of the work produced.

It is anobject of my invention to provide a method of treating aluminumalloys which produces chemical changes in the material 'neces- 6 sary toimprove the physical properties and corrosive resistance thereof withoutcausing such warpage as will require subsequent straightening. Objectsproduced according to my invention are suitable for usewithout further10 working, thus shortening the process and time of production, reducingthe costs, and producing objects of uniform shape and characteristics.

It is an object of my present invention to provide a method of improvingthe physical properties and resistance to corrosion of aluminum alloyswhich consists of first heating the object as desired and thereafterrapidly and evenly extracting the heat from all surfaces thereof.

A further object of my invention is to provide a method of the characterpointed out in the preceding paragraph in which the aluminum or aluminumalloy object after heating is subjected to the action of a heavy vapor,mist, or fog-like atmosphere to efiect the cooling thereof.

It is another object of my invention to provide a method of thecharacter pointed out in the second preceding paragraph in which afterheating the aluminum alloy object it is submitted to the action of aheavy vapor or fog-like atmosphere which substantially simultaneouslycontacts all surfaces thereof.

It is another object of my invention to provide a method of thecharacter pointed out in the third preceding paragraph in which allparts of the object are cooled at substantially the same rate so thatthere will be equal contraction in all areas thereof.

It is a still further object of my invention to provide a method of thecharacter pointed out 40 heretofore in which the aluminum alloy objectis first heated and thereafter subjected to the action of moistureparticles evenly suspended and distributed in an atmosphere, whichmoisture particles contact the surfaces of the ob- Ject and cool sameevenly and rapidly.

It is another object of my invention to provide a method as pointed outin the preceding, objects in which the heavy vapor, mist, fog, ormoisture dispersion in the atmosphere is drawn into contact with thealuminum alloy object to be quenched.

It is also an object of my present invention to provide an apparatuswhereby the process of my invention, the objects of which have beenprises 4.0% copper, 0.15% manganese, 0.5% magnesium', and the remainderaluminum and its normal impurities, and which is commonly known as 17$,for example, it is first raised to a temperature of between 930 and 950F. The

aluminum alloy is held within the specified temperature range for asufficient length of time, depending upon thickness of the metal,heating medium used, and circulation of heating medium, to insure thatall alloying elements are in solution. When the heating step has beencompleted the aluminum alloy is then quenched as rapidly as possiblefrom within this temperature range in order to insure the best possiblephysical properties and corrosion resistance. Adjacent the heatingapparatus I provide a chamber and in and through this chamber Icirculate a fog-like atmosphere, or a heavy mist, or an atmospherehaving liquid particles in substantially even dispersion therein.Immediately upon completing the heating step the aluminum alloy objectis moved into the chamber where it is fully and completely enveloped bythe quenching atmosphere therein and it is rapidly and evenly cooledfrom the temperature range. By such a process t e quenching is quicklydone; that is, a minimum amount of time is lost between heating andquenching medium, and the nature of the quenching medium is such thatthe heat is extracted at a very high rate, thus producing the maximumpercentage of alloying elements in solid solution and in finely dividedand evenly dispersed form throughout the alloy. Furthermore, thequenching operation is such that warpage of such a degree as willrequire straightening of any of the aluminum alloy parts or objects doesnot occur, and the part may be used without further treatment.

In order that those skilled in the art may be instructed in theperformance of my invention a detailed description of a preferred formof the method of my invention and an apparatus for performing the methodwill'be given in connection with the accompanying drawing.

Referring to the drawing.

Fig. 1 is a sectional view showing a furnace, a quenching chamber, andother parts whereby my invention may be practiced.

Fig. 2 is a sectional view through the quenching chamber takemon theline 2--2 of Fi 1.

Fig. 3 is an elevational view of a fog or mist producing or liquiddispersing nozzle which I utilize in the form of my invention shown.

Fig. 4 is a sectional view taken on the line 4-4 of Fig. 3.

Referring to the drawing in detail. the numeral represents a furnacehaving a door l2 which may be opened very quickly and closed veryquickly by common types of mechanism not illustrated. This furnace is ofsuch a design that temperatures within relatively narrow ranges may beproduced in order that aluminum alloy objects may be raised to andmaintained at such a temperature that the alloying elements will beplaced. in solution in the aluminum alloy Parts. For the purpose ofsupporting the obiects both during heating and quenching there isprovided a rack ll having wheels l5 whereby the rack is movable on atrack It in the furnace The rack I4 is essentially a frame constructionso that the objects as illustrated by the numerals i1 and I8 are freelyaccessible from all sides thereof, and so that heat may be applied fromall sides, and so that the cooling medium, as will be pointed outshortly, may be brought into contact with the objects l1 and i8 from allsides thereof.

Placed adjacent the heating furnace II is the quenching apparatus IQ ofmy invention which consists of walls in which are mounted tracks 20 sothat the rack M with the objects l1 and I8 may be run into the quenchingchamber 2|. There is a door 22 at the end of the quenching device I!)adjacent the furnace II, and when the doors 2,2 and I2 are opened therack l4 may be moved along the track l6 and the track 20 and into thequenching chamber 2|. There is a door 23 at the opposite end of thequenching device quenching medium under suitable pressure. De-

pending from the pipes 24 is a multiplicity of nozzles 28 which break upthe liquid from small streams into relatively small particles of evendispersion in order to form an atmosphere of substantially even liquidor moisture dispersion or to form what I term the fog-like atmosphere orheavy mist.

As shown in Figs. 3 and 4, each nozzle is constructed as follows: Thenozzle has a threaded portion 29 which is threadedly secured in anopening of the pipes 24 and has a central passage 30. Formed in the sidewalls of the nozzle is a series of radial downward extending ducts 3|and a series of radial upward extending ducts 32, the outer ends ofwhich meet at an annular channel 33 as illustrated. Near the lower endof the nozzle is a series of downwardly directed ducts 35 formed aroundthe central body projection 36 of the nozzle, and there is also a seriesof outwardly extending ducts 31. The outer ends of the ducts 35 .and 31meet as indicated The water or other quenching medium is suppliedthrough the pipes 24 under a relatively high pressure. This liquid flowsoutwardly through the ducts 3|, 32, 35, and 31 and adjacent streams arebrought into forcible contact with each other, thus breaking the streamsup into small water particles and causing them to fly outwardly in alldirections. This produces the quenching atmosphere 'of my inventionwhich I have defined using various terms in order that thecharacteristics thereof may be understood. The nozzles break up themoisture or liquid into particles which are substantially evenlydispersed in the atmosphere. This produces what I term a fog-likeatmosphere or heavy vapor or mist. Since the nozzles are located in theupper part of the quenching chamber 2|, the quenching chamber 2| isfilled with quenching atmosphere which I have illustrated by amultiplicity of dots in Fig. 2.

The lower wall 40 of the quenching chamber 2| is provided with amultiplicity of outlet openings 42 which communicate between thequenching chamber 2! and an exhaust chamber N. This exhaust chamber 42is connected to an exhaust conduit 44 which is in turn connected to asuction producing means in the form of a suction blower 45 or itsequivalent. To prevent water which has settled from the atmosphere frompassing through the, exhaust apparatus I provide a water pocket 46having a water drain 1, in the lower part of the exhaust chamber 43, andwhich catches water so that it will not pass through the exhaust conduit44.

During the operation of the apparatus and during the performing ofthe-quenching step of my invention the blower 45 is in operation so thatthe quenching atmosphere which is formed by the nozzles 28 is drawndownwardly through the quenching chamber 2| and caused to completelyenvelop the objects l1 and I8. Arrows 49 have been used in Fig. 2 toillustrate the passage of the quenching atmosphere through the quenchingchamber 2| and around the objects I! and IS. The rate of travel of thequenching atmosphere, however, is not so great that the quenchingatmosphere will not be brought into contact with the bottom surfaces ofthe objects II and [8, but on the other hand is sufliciently fast sothat the quenching atmosphere will be continuously brought intoenveloping relationship with the objects.

In performing the process of my invention, the aluminum or aluminumalloy objects I! and I8 are first placed on the rack II in such a mannerthat all surfaces thereof are exposed. Where pieces are laid flat, asindicated at l8, they are supported by a very coarse screen as indicatedin Fig. 2. The rack, including the parts therein, are placed in thefurnace II and the doors thereof are closed. The objects I! and I8 arethen subjected to the suitable heat treating step, the temperature andduration of the treatment depending upon the particular size 'or shapeor characteristics of the objects being treated. The purpose of thisheat treating step is to place in solution the alloying elements of thealuminum alloy, and particularly the copper. The quenching apparatus I9is preferably a portable device which is positioned in front of thefurnace ll just prior to the time that the heat treatment is completed.It is placed in the position shown so that the tracks 20 are inalignment with the tracks l6 of the furnace. When the heating step isfinished the valve 26 is opened and the blower 45 set into operation,thus continuously forming the quenching atmosphere of the characterdefined heretofore in the quenching chamber 2|. The quenching atmosphereis fully establishedbefore the objects are moved into the quenchingchamber. The doors 22 and I2 are then opened and as quickly as possiblethe rack I4 is moved into the quenching chamber 2|, and thereupon thedoors 22 and I2 are immediately closed. In the apparatus which I employI provide a means for moving in the neighborhood of twenty-five secondsor less, the heat must be very rapidly extracted with the result thatconsiderable steam is produced. As the quenching properties of thequenching atmosphere are spent, fresh quenching atmosphere iscontinuously circulated around and in contact with the objects I1 and IIby the action of the suction blower Ii.

When the quenching operation has been completed the valve 26'is closedand the blower l5 shut down. The door 23 may then be opened and the rackI4 removed from the quenching apparatus l9.

The quenching atmosphere forming means has been illustrated as beingpositioned in the upper part of the quenching chamber 2|. It should beunderstood, however, that the quenching atmosphere forming means mightbe remotely lo= ing chamber. The essential element in the proc-- ess isforming the quenching medium and passing it into or through a quenchingchamber in order that the parts or objects to be quenched may beenveloped by the' quenching medium. I believe my invention to be broadlynew and therefore desire it to be broadly construed in accordance withthe appended claims.

I claim as my invention:

1. The method of treating an aluminum alloy which contains at least onealloying element to improve its physical properties and resistance tocorrosion, including the steps of: heating the aluminum alloy to such atemperature and for such period of time as to cause at least a part ofthe alloying element to go into solution;

forming a fog-like quenching atmosphere by improve its physicalproperties and resistance to corrosion, including the steps of: heatingthe aluminum alloy to such a temperature and for such period of time asto cause at least a part of the alloying element to go into solution;forming a fog-like quenching atmosphere by spraying water into aninduced current of air; and

cooling the heated aluminum alloy by substantially simultaneouslycontacting all of the exposed surfaces of said aluminum alloy with saidfog-like quenching atmosphere.

3. The method of treating an aluminum alloy which contains at least onealloying element to improve its physical properties and resistance tocorrosion, including the steps of: heating the aluminum alloy to suchatemperature and for such period of time as to cause at least a part ofthe alloying element to go into solution; forming a fog-like quenchingatmosphere by atomizing water in air; and cooling the heated aluminumalloy by substantially continuously moving such fog-like quenchingatmosphere into contact with substantially all of the exposed surfacesof said aluminum alloy by air currents.

4. The method of treating an aluminum alloy which contains at least onealloying element to improve its physical properties andresistance tocorrosion, including the steps of: heating the aluminum alloy to such atemperature and for such period of time as to cause at least a part ofthe alloying element to go into solution; forming a fog-like quenchingatmosphere containing water particles dispersed therein, by sprayingwater into air; placing said heated aluminum alloy in a quenchingchamber; and cooling the heated aluminum alloy by substantiallysimultaneously contacting all of the exposed surfaces of said aluminumalloy with said fog-like quenching atmosphere; withdrawing steam fromsaid chamber formed by contact of said moisture particles with saidheated aluminum alloy; and replacing said steam by fresh quenchingatmosphere.

5. The method of treating an aluminum alloy which contains at least onealloying element to improve its physical properties and resistance tocorrosion, including the steps of: heating the aluminum alloy to such atemperature and for such period of time as to place at least a part ofthe alloying element in solution; forming a iog-like quenchingatmosphere containing moisture particles dispersed therein, by sprayingwater into air; placing said heated aluminum alloy in a quenchingchamber having an outlet; cooling the heated aluminum alloy bysubstantially simultaneously contacting all of the exposed surquenchingatmosphere;

faces of said aluminum alloy with said fog-like rapidly withdrawingsteam through said outlet formed by contact of said moisture particleswith said heated aluminum alloy; and replacing said steam by freshquenching atmosphere.

6. The method of treating an aluminum alloy which contains at least onealloying element to improve its physical properties and resistance tocorrosion, including the steps of: heating the aluminum alloy to such atemperature and for such period of time as to cause at least a part ofthe alloying element to go into solution; forming a fog-like quenchingatmosphere by spraying water into air adjacent the upper end of aquenching chamber; placing said heated aluminum alloy in said quenchingchamber; cooling the heated aluminum alloy by substantiallysimultaneously contacting all of the exposed surfaces of said aluminumalloy with said fog-like quenching atmosphere; withdrawing steam, formedby contact of said moisture particles with said heated aluminum alloy,through an outlet at the lower end of said chamber; and replacing saidsteam by fresh quenching atmosphere.

'7. The method of treating/a strong aluminum alloy-including the stepsof subjecting the alloy to a solution heat treatment: iorming a foglikequenching atmosphere by atomizing liquid in gaseous medium; and coolingthe alloy by introducing it at substantially the temperature of thesolution heat treatment into; said quenching atmosphere. HARRY HERMANWETZEL.

CERTIFICATE OF CORRECTION. Patent No. 2,17LL,6L;5. October 19 9.

' HARRY HERMAN WETZEL. It is hereby certified that error appears in theprinted specification 'of the above numbered patent requiring correctionas follows: Page 1, second column, line 22; strike out the words"aluminum or"; .and that the said Letters Patent shonld be read withthis correction therein that the same may conform to the record of thecase inthe Patent Office.

Signed and sealed this 19th day of December, A. D. 1959.

Henry Van Arsdale, S Acting Commissioner of Patents.

